What is happening with my rhubarb wine?

[Androshen]

About a month ago I racked my rhubarb wine for the final time and it looked about like a typical white wine.
Since then it has been slowly darkening ...
I added absolutely *nothing* but it is now about the color of an ice tea.
Any ideas why this would happen?

 

[Yooper]

Oxidation will do that. If you have headspace, or the airlock dried out, it could turn brown due to the oxidation.